I. Field
The following description relates generally to communications in a multiple-input-multiple-output network and more particularly to Single Frequency Network (SFN) transmission of a Distributed Reference Signal (DRS) through layer-specific channelization.
II. Background
Wireless communication systems are widely deployed to provide various types of communication content such as voice, data, and so on. These systems may be multiple-access systems capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth and transmit power). Examples of such multiple-access systems include Code Division Multiple Access (CDMA) systems, Time Division Multiple Access (TDMA) systems, Frequency Division Multiple Access (FDMA) systems, 3GPP Long Term Evolution (LTE) systems, and Orthogonal Frequency Division Multiple Access (OFDMA) systems. As demand for high-rate and multimedia data services rapidly grows, there is a challenge to implement efficient and robust communication systems with enhanced performance.
Generally, a wireless multiple-access communication system can simultaneously support communication for multiple wireless terminals. Each terminal communicates with one or more base stations through transmissions on forward and reverse links. Forward link (or downlink) refers to communication link from the base stations to the terminals, and reverse link (or uplink) refers to communication link from the terminals to the base stations. Communication links may be established through a single-in-single-out (SISO) system, a multiple-in-single-out (MISO) system, or a multiple-in-multiple-out (MIMO) system.
A MIMO system employs multiple (NT) transmit antennas and multiple (NR) receive antennas for data transmission. A MIMO channel formed by NT transmit and NR receive antennas may be decomposed into NS independent channels, which are also referred to as spatial channels, where NS≦min{NT, NR}. Each of the NS independent channels corresponds to a dimension. MIMO systems can provide improved performance (e.g., higher throughput, greater reliability, and so forth) if additional dimensionalities created by multiple transmit and receive antennas are utilized.
MIMO systems support Time Division Duplex (TDD) and/or Frequency Division Duplex (FDD) systems. In a TDD system, forward and reverse link transmissions are on the same frequency region so that the reciprocity principle allows estimation of the forward link channel from the reverse link channel. This enables the access point to extract transmit beamforming gain on the forward link when multiple antennas are available at the access point.